Sarika Singh

Surface engineered magnetic nanoparticles for removal of toxic metal ions and bacterial pathogens.

Surface engineered magnetic nanoparticles (Fe(3)O(4)) were synthesized by facile soft-chemical approaches. XRD and TEM analyses reveal the formation of single-phase Fe(3)O(4) inverse spinel nanostructures. The functionalization of Fe(3)O(4) nanoparticles with carboxyl (succinic acid), amine (ethylenediamine) and thiol (2,3-dimercaptosuccinic acid) were evident from FTIR spectra, elemental analysis and zeta-potential measurements. From TEM micrographs, it has been observed that nanoparticles of average sizes about 10 and 6 nm are formed in carboxyl and thiol functionalized Fe(3)O(4), respectively. However, each amine functionalized Fe(3)O(4) is of size ~40 nm comprising numerous nanoparticles of average diameter 6 nm. These nanoparticles show superparamagnetic behavior at room temperature with strong field dependent magnetic responsivity. We have explored the efficiency of these nanoparticles for removal of toxic metal ions (Cr(3+), Co(2+), Ni(2+), Cu(2+), Cd(2+), Pb(2+) and As(3+)) and bacterial pathogens (Escherichia coli) from water. Depending upon the surface functionality (COOH, NH(2) or SH), magnetic nanoadsorbents capture metal ions either by forming chelate complexes or ion exchange process or electrostatic interaction. It has been observed that the capture efficiency of bacteria is strongly dependent on the concentration of nanoadsorbents and their inoculation time. Furthermore, these nanoadsorbents can be used as highly efficient separable and reusable materials for removal of toxic metal ions.

Fe3O4 embedded ZnO nanocomposites for the removal of toxic metal ions, organic dyes and bacterial pathogens

We report a facile soft-chemical approach for the fabrication of Fe3O4 embedded ZnO magnetic semiconductor nanocomposites (Fe3O4–ZnO MSN), and investigate and compare their efficacy for the detoxification of water with respect to their individual counterparts (Fe3O4 and ZnO). The formation of Fe3O4–ZnO MSN was evident from the detailed structural analyses by XRD, TEM and magnetic measurements. It has been observed that these nanocomposites have a strong tendency for the simultaneous removal of Ni2+, Cd2+, Co2+, Cu2+, Pb2+, Hg2+ and As3+ from waste-water due to their porous network structure, surface polarity and high surface area. These nanocomposites also show a good photocatalytic activity for the degradation of organic dyes under UV irradiation, and are found to be efficient in the easy and rapid capturing of bacterial pathogen. It has been observed that the efficiency of capturing bacteria is strongly dependent on the concentration of nanoadsorbents and their inoculation time. It is investigated that these nanoadsorbents can be used as highly efficient separable and reusable materials for the simultaneous removal of toxic metal ions, organic dyes and bacterial pathogen.

Carboxyl decorated Fe3O4 nanoparticles for MRI diagnosis and localized hyperthermia

We report the development of carboxyl decorated iron oxide nanoparticles (CIONs) by a facile soft-chemical approach for magnetic resonance imaging (MRI) and hyperthermia applications. These superparamagnetic CIONs (~10 nm) are resistant to protein adsorption under physiological medium and exhibit good colloidal stability, magnetization and cytocompatibility with cell lines. Analysis of the T2-weighted MRI scans of CIONs in water yields a transverse relaxivity (r2) value of 215 mM(-1) s(-1). The good colloidal stability and high r2 value make these CIONs as promising candidates for high-efficiency T2 contrast agent in MRI. Further, these biocompatible nanoparticles show excellent self-heating efficacy under external AC magnetic field (AMF). The infrared thermal imaging confirmed the localized heating of CIONs under AMF. Thus, these carboxyl decorated Fe3O4 nanoparticles can be used as a contrast agent in MRI as well as localized heat activated killing of cancer cells. Furthermore, the active functional groups (COOH) present on the surface of Fe3O4 nanoparticles can be accessible for routine conjugation of biomolecules/drugs through well-developed bioconjugation chemistry.

Functional Oxide Nanomaterials and Nanocomposites for the Removal of Heavy Metals and Dyes

Water scarcity and its contamination with toxic metal ions and organic dyes represent a serious worldwide problem in the 21st century. A wide range of conventional approaches have been used to remove these contaminants from waste. Recently, nanotechnology has been given great scope for the fabrication of desirable nanomaterials with large surface-to-volume ratios and unique surface functionalities to treat these pollutants. Amongst these, oxide-based nanomaterials emerge as promising new materials for water purication. In this review article, we explore a broad-spectrum overview of recent developments in the area of oxide-based nanomaterials, such as Fe3O4, ZnO and TiO2, as well as their binary and ternary nanocomposites, for the removal of various toxic metal ions and organic dyes. The possible adsorption mechanism and the surface modification of adsorbents for the removal of heavy metal ions and dyes are discussed in detail. The sorption properties of the different adsorbents depend on the surface functionalization of nanomaterials, the pH of the medium, and the reaction time and concentration, etc. In addition, we provide a short overview on the study of the selective adsorbents in multi-component sorption systems, along with the future prospects of oxide nanomaterials in water purification.

Shape-controlled hierarchical ZnO architectures: photocatalytic and antibacterial activities

A simple soft chemical approach has been successfully adopted for the synthesis of ZnO in spherical assemblies (SA), nanorods assemblies (NRA), cauliflower-like assemblies (CFA) and mushroom-like assemblies (MA). The morphology of self-assembled ZnO nanostructures composed of numerous nanocrystals has been confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction and optical studies suggest an anisotropic nature of ZnO and presence of structural defects in ZnO nanostructures, respectively. N2 adsorption–desorption isotherm curves of these nanostructures (except MA) indicate predominantly 3D-mesoporous nature. These nanostructures are useful for their potential application in photocatalytic degradation of organic dyes (e.g. methylene blue, Rhodamine B) and inhibition of bacterial growth (S. aureus). Among these ZnO architectures, CFA exhibits excellent photocatalytic and antibacterial activities. In addition, the inhibition of bacterial growth of S. aureus is more effective under UV light than in dark conditions.

OPTIMIZATION OF THE PARAMETERS FOR DECOLOURIZATION BY ASPERGILLUS NIGER OF ANAEROBICALLY DIGESTED DISTILLERY SPENTWASH PRETREATED WITH POLYALUMINIUM CHLORIDE

Molasses spentwash from distilleries is characterized by high COD and colour. The fungal decolourization of anaerobically digested molasses spentwash requires significant dilution. In this study, decolourization by Aspergillus niger isolate IITB-V8 was performed on polyaluminium chloride (PAC) treated anaerobically digested spentwash without dilution of wastewater. Optimization of parameters was studied using statistical experimental designs. In the first step, Plackett-Burman design was used for screening the important parameters. Glucose was taken as the carbon source for the growth of A. niger. KH(2)PO(4) and pH were found to be the important factors affecting decolourization. In the second step, Box-Behnken design was used to determine the optimum level of each of the significant parameters. A second-order polynomial was determined by the multiple regression analysis of the experimental data. The optimum values for the important factors to achieve maximum decolourization of 68.4% were 5.5 g/L Glucose, 1.2 g/L KH(2)PO(4) and 5 pH. The determination coefficient (R(2)) was 0.9973, which ensures adequate credibility of the model. The total decolourization obtained after fungal treatment was 86.8% which indicates fungal decolourization after pretreatment with PAC is a viable option for the treatment of digested molasses spentwash.

Catalytic and antibacterial activity of Ag decorated magnetic core shell nanosphere

We report a facile approach for the preparation of Ag nanoparticles decorated magnetic Fe3O4@SiO2 core shell nanosphere (Ag-MCN) and investigated its potential application for the catalytic reduction of organic pollutants and inhibition of bacterial pathogens. The successful formation of Ag-MCN was confirmed by X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The average size of this nanosphere was found to be 85nm and it exhibits superparamagnetic behavior at room temperature. These nanospheres even at low concentration and short incubation period showed good catalytic performance for the reduction of Rhodamine B (RhB) and 4-nitrophenol (4-NP). Further, these magnetic nanosphere possess good antibacterial activity for Gram negative, Escherichia coli (E. coli). Ag-MCN are found to be efficient for complete inhibition of E. coli at a concentration of 50mgL(-1) after incubation for a period of 3h. Furthermore, the generation of reactive oxygen species (ROS) by nanosphere and its effect in the antibacterial activity has been investigated. These nanospheres exhibit good colloidal stability, recycling capability, and could be easily separated from solution via external magnet.